It is well known to construct motor vehicle body doors, hoods, fenders, tailgates, and trunk and deck lids by stamping an outer sheet metal panel and separately stamping an inner sheet metal reinforcing panel with an outer periphery generally matching that of the outer panel, and then joining the two panels together by hemming the periphery of the outer panel over an adjacent edge of the inner panel to thereby secure the panels together. The inner and outer panels are individually stamped to their desired size and shape, with the outer panel being slightly larger than the inner panel to provide a border flange portion along the edge of the outer panel having an upstanding lip which can be folded over the peripheral edge of the inner panel to define the hem flange which connects the two panels.
Of particular difficulty is the hemming of an inside perimeter such as about the periphery of a window of a vehicle door. Previously, the hemming of a window opening was performed in two or more forming operations in at least two separate forming stations. The first station hemmed a portion of the window perimeter and the second station was necessary to hem the voids or areas not hemmed by the first station such as at the corners of the window and also at the location of any gaps between the hemming steels of the first station apparatus. This not only requires the initial cost of two different hemming machines, but also increases the time to completely hem an inside perimeter such as for a window opening and increases the number of work stations the door or other sheet metal component must be transferred to thereby increasing the likelihood of damaging the door during its manufacture and the cost of tooling for and making the door.